Method of producing fuel cell-use separator and device for producing it

ABSTRACT

A fuel cell separator manufacturing method including the steps of removing an abnormal layer ( 91 ) arising at the surface layer of a metal material for use as a separator ( 20 ) when it is rolled, a exposing portions of conductors ( 92 ) included in a surface layer part of the metal material itself to project, and carrying out a passivation treatment on the surface layer part of the metal material itself. The steps of removing the abnormal layer and exposing portions of the conductors are possible in the same process, chemically or electro-chemically. Therefore, the number of steps can be cut and increased productivity and reduced cost of separators can be achieved.

TECHNICAL FIELD

This invention relates to a fuel cell separator manufacturing method andmanufacturing apparatus suitable for achieving productivity improvement,cost reduction, quality improvement and quality stabilization of a metalseparator.

BACKGROUND ART

In solid high polymer electrolyte fuel cell units, because they are of astructure such that the desired output is obtained by stacking togethermultiple fuel cells, for the separators that divide these fuel cells,metal materials, which compared to polymer materials are stronger withrespect to pressure applied at the time of stacking and are advantageousto size reduction after stacking, are seen as leading.

Known fuel cells employing metal separators of this kind include forexample {circle over (1)} JP-A-8-180883, “Solid High Polymer ElectrolyteFuel Cell” (hereinafter, Related Art {circle over (1)}), {circle over(2)} JP-A-2000-164228, “Solid High Polymer Electrolyte Fuel CellSeparator and Manufacturing Method Thereof” (hereinafter, Related Art{circle over (2)}).

In Related Art {circle over (1)}, a single cell of a fuel cell isdisclosed wherein electrode films are disposed on both sides of a solidhigh polymer electrolyte film, these electrode films are sandwiched withfor example stainless steel separators, and the edge parts of theseparators are sealed with seals.

In Related Art {circle over (2)}, a single cell of a fuel cell isdisclosed wherein an anode electrode and a cathode electrode aredisposed on either side of a solid high polymer film, and the anodeelectrode and the cathode electrode are sandwiched by separators withfor example stainless steel as their base material.

In the technology of the publications of Related Art {circle over (1)}and {circle over (2)}, when for example cold rolling is carried out onstainless steel to become the material of a separator to bring thestainless steel to a predetermined thickness, at the surface layer partof the stainless steel, as a result of the rolling, an abnormal layermade up of oxides and of intermetallic compounds which had been includedin the stainless steel sheet, crushed to a small particle size, isformed. Because the conductivity of this abnormal layer is not good, tomake the electrical contact resistance of the separator small it isnecessary for it to be removed.

To do this, a separator manufacturing method having a step of removingan abnormal layer of stainless steel like this has been conceived. Thistechnology will be described below.

With reference to FIG. 21 the main points of the manufacture of a metalseparator of related art will be explained in order.

1. Abnormal Layer Removal

A metal material 400 to constitute the material of a separator is rolledbefore being press-formed to a predetermined shape. When the metalmaterial 400 is rolled, an abnormal layer 401 is formed at the surfacelayer of the metal material 400.

2. Abnormal Layer Removal Etching

The above-mentioned abnormal layer 401 is removed by etching.

3. First Passivation Treatment

To prevent corrosion of the surface of the metal material 400, a firstpassivation treatment is carried out and a first passivation film 402 isformed.

4. Exposure Etching

Because particulate conductors 403 . . . ( . . . denotes a plurality.The same applies hereinafter.) consisting of the above-mentionedintermetallic compounds naturally included in the metal material 400 aregood electrical conductors, with the object of reducing the electricalcontact resistance between the separator and an adjacent separator orelectrode when the metal material 400 is made a separator and stacked ina fuel cell, exposing of the conductors 403 . . . is carried out. Toperform this exposing, etching is carried out.

5. Second Passivation Treatment

After the exposing of the conductors 403 . . . , so that the surface ofthe metal material 400 does not corrode a second passivation treatmentis carried out, and a second passivation film 405 is formed.

This completes the manufacture of the separator.

The separator manufacturing method described above will be explained indetail with reference to FIG. 22. STXXX indicates a step number.

ST101 A metal material press-formed after rolling is degreased. Theprocess liquid is an aqueous surfactant solution, the treatmenttemperature is 30° C., and the treatment time is 1 minute.

ST102 The metal material is washed. The treatment time is 1 minute.

ST103 The abnormal layer formed at the time of rolling is removed byetching. The process liquid is a solution of aqua regia and asurfactant, the treatment temperature is 98° C., and the treatment timeis 60 minutes.

ST104 The metal material is washed. The treatment time is 1 minute.

ST105 To prevent corrosion of the surface of the metal material, a firstpassivation treatment is carried out. The process liquid is 50% nitricacid, the treatment temperature is 50° C. and the treatment time is 30minutes.

ST106 The metal material is washed. The treatment time is 1 minute.

ST107 An etching is carried out to expose the conductors in the metalmaterial. The process liquid is a solution of 20% nitric acid and 8%hydrofluoric acid, the treatment temperature is 30° C. and the treatmenttime is 10 minutes.

ST108 The metal material is washed. The treatment time is 1 minute.

ST109 To prevent corrosion of the surface of the metal material a secondpassivation treatment is carried out. The process liquid is 50% nitricacid, the treatment temperature is 50° C. and the treatment time is 30minutes.

ST110 The metal material is washed. The treatment time is 1 minute.

ST111 The metal material is dried. The treatment time is 1 minute.

This completes the manufacture of the separator. The total process timeis 137 minutes.

In the separator manufacturing method described above, by the abnormallayer being removed chemically by etching, and by exposing of theconductors also being carried out by etching, the contact resistance ofthe separator is made small.

However, in the above-mentioned FIG. 22, the required time from thedegreasing of ST101 to the drying of ST111 is 137 minutes in total, andbecause the number of process steps is large the number of differentprocess liquids and the number of process tanks for holding the processliquids are large and much labor is taken in the temperature managementof the process liquids, and consequently, to achieve productivityimprovement and cost reduction of metal separators, a reduction in theabove-mentioned number of process steps has been needed.

When in the above-mentioned ST103 the intended abnormal layer removaletching is not effected, an abnormal layer remains at the surface layerof the metal material, and it is likely that this will affect theconductor exposure etching of ST107 and exposing of the conductors willnot be fully effected, and when exposing of the conductors is notsufficient, when the manufactured separator is stacked in the assemblyof a fuel cell, the electrical contact resistance between separators orbetween separators and electrodes will be large and a sufficient outputof the fuel cell will not be obtained. This is the same when theintended exposing of conductors is not effected in ST107.

To avoid this, if it can be checked during the separator manufacturingprocess described above whether or not the intended treatment has beeneffected, the quality of the separators can be increased and the qualityof the separators can be stabilized, and when the intended processinghas not been carried out on a metal material the waste of continuingprocessing with subsequent steps can also be eliminated.

Also, the following kind of metal separator manufacturing method will bedescribed.

FIG. 23 shows a process tank 411 filled with a process liquid 412 and ametal material 414 (a material to eventually become a separator) held ina frame-shaped member 413 immersed in this process liquid 412. 415 is awire suspending the frame-shaped member 413.

In a fuel cell, the separator accounts for most of the cost. This isbecause the separator requires a structure finely formed with flowpassages for fuel gas and oxidant gas and cooling water, and surfacetreatment to prevent corrosion by electrolytes. Accordingly, if theproductivity of the separators is raised and their cost reduced, thecost of fuel cells is greatly reduced and a contribution is made to thespread of fuel cell vehicles.

In FIG. 23, for example when the metal material 414 is treated with theprocess liquid 412 of the above-mentioned process tank 411, (1) toquicken the treatment of the metal material 414 and also to effect ituniformly, it is effective to agitate the process liquid 412 with anagitating device, but when there are multiple process tanks 411, anagitating device must be provided for each of them, leading to increasedcost, and (2) if the carrying of the metal material 414 to the processtanks 411 and the holding of the metal material 414 for the immersion ofthe carried metal material 414 in the process liquid 412 are notcoordinated well, the flow of the production process cannot be madesmooth, and the production time increases, and (3) if the number ofmetal materials processed at once is low, the number of units producedper unit time is low, and if this can be improved, productivityimprovement and cost reduction of separators can be achieved.

DISCLOSURE OF THE INVENTION

It is an object of the invention to achieve productivity improvement,cost reduction, quality improvement and quality stabilization of metalseparators, and to eliminate waste in the manufacturing process.

In a first aspect, the invention provides a fuel cell separatormanufacturing method comprising an abnormal layer removing step ofremoving an abnormal layer arising at the surface layer of a metalmaterial to be used as a separator when it is rolled; a conductorexposing step of causing portions of conductors included in a surfacelayer part of the metal material itself to project; and a passivationtreatment step of carrying out a passivation treatment on the surfacelayer part of the metal material itself.

The removing of the abnormal layer with the abnormal layer removing stepand the removing of the surface layer part of the separator with theconductor exposing step are possible in the same process, chemically orelectro-chemically, and the number of steps can be cut and increasedproductivity and reduced cost of separators can be achieved.

Preferably, the method of the invention comprises: a step of rolling ametal material with rolling means; a step of forming the rolled materialto a predetermined shape with pressing means; the abnormal layerremoving step and the conductor exposing step carried out by etching;and the passivation treatment step, and the abnormal layer removal stepand the conductor exposing step are carried out in a single etching.

By performing in one etching process the abnormal layer removal andexposing of conductors which in related art have been carried out inseparate etching processes, the number of steps in the process can bereduced and the productivity of metal separators can be raised and theirmanufacturing cost cut.

Preferably, the above-mentioned etching process is carried out with thetemperature and composition of the etching liquid selected incorrespondence with the state of the abnormal layer.

By selecting constituents with a stronger abnormal layer removing actionas the constituents of the etching liquid and raising the temperature ofthe etching liquid when the abnormal layer is formed thick to the extentthat conductors cannot be confirmed by visual observation, and selectingconstituents with a weaker abnormal layer removing action as theconstituents of the etching liquid and making the temperature of theetching liquid low when the abnormal layer is formed thin to the extentthat conductors can be confirmed by visual observation, it is possibleto carry out the manufacture of a metal separator efficiently.

Preferably, the etching is carried out with the agitation method changedin correspondence with the state of the abnormal layer.

By making the etching liquid agitation speed high and making theagitation time long when the abnormal layer is formed thick to theextent that conductors cannot be confirmed by visual observation, andmaking the etching liquid agitation speed low and making the agitationtime short when the abnormal layer is formed thin to the extent thatconductors can be confirmed by visual observation, it is possible tocarry out the manufacture of a metal separator efficiently.

Preferably, the etching is carried out with the concentration of theetching liquid changed in correspondence with the state of the abnormallayer.

By making the etching liquid concentration high when the abnormal layeris formed thick to the extent that conductors cannot be confirmed byvisual observation and making the etching liquid concentration low whenthe abnormal layer is formed thin to the extent that conductors can beconfirmed by visual observation, it is possible to carry out themanufacture of a metal separator efficiently.

Preferably, the etching is carried out in a liquid tank selected fromamong a plurality of liquid tanks holding etching liquids of differentcompositions.

By for example selecting a liquid tank with the etching liquidconcentration raised or the etching liquid concentration and temperatureboth raised when the abnormal layer is formed thick to the extent thatconductors cannot be confirmed by visual observation and for exampleselecting a liquid tank with the etching liquid concentration weakenedor the etching liquid concentration weakened and the temperature loweredwhen the abnormal layer is formed thin to the extent that conductors canbe confirmed by visual observation, it is possible to carry out themanufacture of a metal separator efficiently.

Preferably, the removal of the abnormal layer is promoted by a granularmaterial being mixed with the etching liquid and the etching liquidbeing agitated.

With a granular material it is possible to quicken the removal of theabnormal layer and shorten the treatment time.

Preferably, the method of the invention comprises: the abnormal layerremoving step; a first checking step of checking the weight of the metalmaterial after the abnormal layer is removed; a first passivationtreatment step of carrying out a passivation treatment for corrosionresistance on the metal material; the conductor exposing step carriedout by etching; a second checking step of checking the weight of themetal material after this step; and a second passivation treatment stepof carrying out a passivation treatment again after this, andconfirmation of the respective weights is carried out in the firstchecking step and the second checking step.

If the weight of the metal material measured in the first checking stepand its weight before the abnormal layer removal are compared, theweight of abnormal layer removed can be confirmed, and if the weight ofthe metal material measured in the second checking step and the weightmeasured in the first checking step are compared, an exposure weightconstituting a weight of metal material removed to expose the conductorscan be confirmed, and an improvement in the quality of the metalmaterial and stabilization of the quality can be achieved.

Preferably, the first checking step and the second checking step arecarried out after the metal material is washed and dried.

By the first checking step and the second checking step being carriedout after the metal material is washed and dried, adhered matter adheredto the metal material surface can be removed, and the measurementaccuracy of the weight of the metal material in the first checking stepand the second checking step can be raised.

Preferably, in the case of a metal material whose weight obtained in thefirst checking step or the second checking step falls outside apredetermined range, the subsequent steps are not carried out.

By not carrying out subsequent steps on a metal material whose weightobtained in the first checking step or the second checking step felloutside a predetermined range, it is possible to eliminate the waste ofcarrying out steps on that metal material after the first checking stepor the second checking step.

Preferably, the determination of whether or not the weight obtained inthe first checking step and the second checking step is within apredetermined range is carried out by automatic determining means.

By carrying out the determination of whether or not the weight obtainedin the first checking step and the second checking step is within apredetermined range by automatic determining means, it is possible toachieve automation of the checking steps, and, for example if thecarrying of the metal material is also automated, the metal materialmanufacturing process can be made unmanned.

Preferably, a separator is manufactured from: a step of press-formingthe metal material to a predetermined shape; a step of holding aplurality of such formed metal materials on cylindrical holding jig; astep of immersing the held metal materials in a process liquid containedin a process tank and agitating the process liquid with the metalmaterial by driving the cylindrical holding jig with driving means; theabnormal layer removing step; the conductor exposing step; thepassivation treatment step; and a step of removing the metal materialsfrom the process tank and drying them.

By agitating the process liquid with the metal materials by driving thecylindrical holding jig, the treatment of the metal materials can bequickened and the treatment can be carried out uniformly. Therefore,separators of superior quality can be manufactured efficiently.

Because the metal materials can be carried to the process tanks with thecylindrical holding jig, and the holding of the metal materials, thecarrying and the agitation can be carried out continuously without themetal materials being removed part-way through the production process,the separator production time can be shortened.

Also, multiple metal materials held on the cylindrical holding jig canbe processed at once, and the number of units produced can be increased.

Thus, by means of these improvements the productivity of separators canbe raised and the cost of separators can be lowered.

Preferably, the metal materials are held by being fitted in framemembers provided on an outer face of the cylindrical holding jig.

By the metal materials being held by being fitted in frame members,larger areas of the surfaces of the metal materials can be processed,and the metal materials can be treated effectively.

Preferably, it is made up of: a step of rolling the metal material withrolling means; a step of forming the rolled material to a predeterminedshape with pressing means; the abnormal layer removing step; theconductor exposing step; and the passivation treatment step, and theabnormal layer removing step and the conductor exposing step are carriedout by electrolytic etching and this electrolytic etching step and thepassivation treatment step are carried out consecutively usingelectrical potential control.

Whereas in related art the removal of the abnormal layer of the metalmaterial for use as a separator and the exposing of conductors and thepassivation treatment have been carried out in separate steps, in thisinvention, by performing them consecutively using electrical potentialcontrol, the number of steps in the process can be reduced and theprocess time can be shortened and the productivity of metal separatorscan be raised and their manufacturing cost cut.

Preferably, the potential control, when the metal material is made ananode and an electrode facing this anode is made a cathode, makes thepotential difference between the anode and the cathode large in theelectrolytic etching and makes the potential difference between theanode and the cathode small in the passivation treatment.

By making the potential difference large and creating a super-passivestate at the time of the electrolytic etching it is possible to make theabnormal layer of the metal material and the surface layer part of themetal material itself easy to remove and make the exposing of theconductors easy, and by making the potential difference small andcreating a passive state at the time of the passivation treatment it ispossible to make the formation of a passivation film on the metalmaterial easy.

Preferably, in the electrolytic etching, as well as the potentialdifference between the anode and the cathode being made large, thecurrent density is kept constant.

Whereas for example when the potential difference is made large and alsothe potential difference is made constant, as the electrolytic etchingtime elapses, a film in the super-passive region is gradually formed onthe surface of the metal material, and current ceases to flow and theelectrolytic etching reaction slows down, by potential control beingcarried out so as to keep the current density constant as in thisinvention, the electrolytic etching reaction can be kept going well.

A second aspect of the invention provides a fuel cell separatormanufacturing apparatus for manufacturing a separator by press-forming arolled metal material to a predetermined shape and using etching toremove an abnormal layer arising in the metal material in the rollingand carry out exposing to cause portions of conductors included in asurface layer part of the metal material itself to project and carryingout a passivation treatment on the surface layer part of the metalmaterial itself, the manufacturing apparatus comprising: a degreasingtank for degreasing the rolled metal material; an etching tank forcarrying out the etching; a passivation treatment tank for carrying outthe passivation treatment; cleaning tanks for removing respectiveprocess liquids from the metal material after the degreasing, after theetching and after the passivation treatment; a carrying apparatus forcarrying the metal material to these tanks; a driving device for drivingthe metal material to agitate the process liquids in the tanks with thecarried metal material itself, and a control unit for controlling thecarrying apparatus and the driving device.

Compared to related art a separator can be manufactured with a simplerconstruction, and the cost of the separator manufacturing apparatus canbe reduced.

Preferably, the manufacturing apparatus comprises an abnormal layerremoval tank for removing the abnormal layer, a passivation treatmenttank for carrying out the passivation treatment, a conductor exposingtank for carrying out the exposing of conductors, weight measuring meansfor measuring the weight of the metal material after the abnormal layerremoval and after the conductor exposure, and automatic determiningmeans for determining on the basis of weight information from thisweight measuring means whether or not the weight is in a predeterminedrange.

After the metal material abnormal layer removal or after the conductorexposure, for example, when it is determined by the automaticdetermining means that the weight of the metal material measured by theweight measuring means is not within a predetermined range, that metalmaterial can be removed from the production process, and it is possibleto stably manufacture separators of good quality only.

Because metal materials whose weight is not within a predetermined rangeare removed from the production process, the waste of continuing themanufacture of those metal materials can be eliminated.

Preferably, the manufacturing apparatus comprises an etching tank forcarrying out etching, a passivation treatment tank for carrying outpassivation treatment, a cylindrical holding jig provided with framemembers on an outer face thereof to hold a plurality of metal materialsto be processed in the etching tank and the passivation treatment tank,driving means for driving the cylindrical holding jig to agitate processliquids of the etching tank and the passivation treatment tank with themetal materials held in this cylindrical holding jig, and carrying meansfor carrying the cylindrical holding jig to the etching tank and thepassivation treatment tank.

The cylindrical holding jig holding the metal materials can be used bothas a metal material carrying tool and as a process liquid agitatingtool, and compared to a case wherein these functions are performed byseparate devices the number of parts can be reduced and the cost of theseparator manufacturing apparatus can be reduced. And, because multiplemetal materials can be held, carried, and agitated at once, theproductivity of separators can be raised and the cost of separators canbe lowered.

Preferably, the manufacturing apparatus comprises a process tank filledwith a process liquid and having an electrode provided in the processliquid to electrolytically etch the metal material, electricity supplymeans for supplying electricity between a metal material immersed in theprocess liquid in this process tank and the electrode, current densitydetecting means for detecting the current density during the supply ofelectricity with this electricity supply means, potential control meansfor controlling the potential difference between the metal material andthe electrode in correspondence with the current density detected bythis current density detecting means, and a timer for sending a timesignal to the potential control means to effect electricity supply for apredetermined time.

Compared to related art, separators can be manufactured with a simpleconstruction, and the cost of the separator manufacturing apparatus canbe reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a fuel cell separator manufacturingapparatus according to a first embodiment of the invention;

FIG. 2 is a view illustrating a separator treatment state of the firstembodiment of the invention;

FIG. 3 is a view illustrating main processes in the separatormanufacturing method of the first embodiment of the invention;

FIG. 4 is a flowchart illustrating the separator manufacturing method ofthe first embodiment of the invention;

FIG. 5 is a flowchart illustrating a variation of the separatormanufacturing method of the first embodiment of the invention;

FIG. 6 is a view illustrating a fuel cell separator manufacturingapparatus according to a second embodiment of the invention;

FIG. 7 is a flowchart illustrating a separator manufacturing methodaccording to the second embodiment of the invention;

FIG. 8A through FIG. 8C are first action views illustrating theseparator manufacturing method of the second embodiment of theinvention, FIG. 8A being a sectional view showing an abnormal layerformed on a separator workpiece, FIG. 8B being a sectional view showingthe abnormal layer removed and conductors exposed, and FIG. 8C being asectional view showing a passivation film formed on the separatorworkpiece;

FIG. 9A through FIG. 9D are second action views illustrating theseparator manufacturing method of the second embodiment of theinvention, FIG. 9A being an enlarged sectional view of a main part ofthe separator workpiece, FIG. 9B being a view seen with a metalmicroscope of the surface of the separator workpiece in a range wherethe thickness of the abnormal layer is T1 to T2, FIG. 9C being a viewseen with a metal microscope of the surface of the separator workpiecein a range where the thickness of the abnormal layer is T2 to T3, andFIG. 9D being a view seen with a metal microscope of the surface of theseparator workpiece in a range where the thickness of the abnormal layeris below T3 and exceeds T=0;

FIG. 10 is an operation view illustrating a variation of etchingconditions of the second embodiment of the invention;

FIG. 11 is a view illustrating a fuel cell separator manufacturingapparatus according to a third embodiment of the invention;

FIG. 12 is a side view of a cylindrical holding jig according to thethird embodiment of the invention;

FIG. 13 is a perspective view of a cylindrical holding jig according tothe third embodiment of the invention;

FIG. 14A and FIG. 14B are perspective views illustrating details of thecylindrical holding jig of the third embodiment of the invention, FIG.14A being a perspective view showing a top fitting member before it isfitted to a frame proper, and FIG. 14B being a perspective view showingthe top fitting member after it is fitted to a frame proper;

FIG. 15 is a view illustrating a separator treatment state of the thirdembodiment of the invention;

FIG. 16 is a view illustrating a fuel cell separator manufacturingapparatus according to a fourth embodiment of the invention;

FIG. 17 is a view illustrating a separator treatment state of the fourthembodiment of the invention;

FIG. 18 is a flowchart showing a separator manufacturing methodaccording to the fourth embodiment of the invention;

FIG. 19 is a graph illustrating the separator manufacturing method ofthe fourth embodiment of the invention;

FIG. 20 is a block diagram illustrating main parts of the separatormanufacturing apparatus of the fourth embodiment of the invention;

FIG. 21 is a view illustrating the main points of metal separatormanufacture of related art;

FIG. 22 is a flowchart illustrating a metal separator manufacturingprocess of related art; and

FIG. 23 is a view illustrating treatment of a surface in the manufactureof a metal separator in related art.

BEST MODE FOR CARRYING OUT THE INVENTION

As shown in FIG. 1, a separator manufacturing apparatus 10 is made up ofprocess tanks 11 holding process liquids for carrying out treatmentswhich will be further discussed later, a dryer 17 for carrying outdrying, a carrying apparatus 21 for carrying a separator workpiece 20 tothe positions of the process tanks 11 . . . and the dryer 17, a drivingdevice 22 for driving an electric motor to raise and lower a separatorworkpiece 20 being moved by this carrying apparatus 21, lifters 31 . . .for raising and lowering the process tanks 11 . . . to immerse theseparator workpiece 20 in the process liquids, liquid temperatureadjusting devices 41 . . . (although each of the process tanks 11 . . .is provided with one of these liquid temperature control devices 41, inthe figure one is only drawn on one process tank 11), and a control unit42 for controlling the dryer 17, the carrying apparatus 21, the drivingdevice 22, the lifters 31 . . . and the liquid temperature controldevices 41. 31 d are lifter drivers for driving the lifters 31 . . . .

The process tanks 11 . . . are lined up in correspondence with stepsshown in FIG. 4 and FIG. 5 (except for weighing steps and drying steps)which will be described later, and for example the leftmost process tank11 in the figure is a process tank for a degreasing step constituting afirst step in the production process.

The separator workpiece 20 is eventually made into a separator by theseparator manufacturing apparatus 10, and is made by rolling a metalmaterial, for example stainless steel (particularly austenite stainlesssteel) into a thin sheet and then press-forming channels and holes in itfor passing fuel gas, oxidant gas and cooling water in a fuel cell.

The dryer 17 is a device operated and stopped by an ON/OFF signal fromthe control unit 42, and dries the separator workpiece 20 for example byfanning or by radiating heat at the separator workpiece 20.

The carrying apparatus 21 is disposed above the process tanks 11 . . .and the dryer 17 and is made up of a first drum 44 driven by a firstelectric motor 43, a second drum 46 driven by a second electric motor45, a cable 47 running between the first drum 44 and the second drum 46,a separator carrying part 48 attached to this cable 47, and a weightsensor 49 serving as weighing means for measuring the weight of theseparator workpiece 20.

To carry the separator workpiece 20, the first electric motor 43 and thesecond electric motor 45 are rotated synchronously by the control unit42 to rotate the first drum 44 and the second drum 46 and move theseparator carrying part 48, from which the separator workpiece 20 issuspended.

In FIG. 2 a state is shown wherein with respect to a separator workpiece20 for example a lifter 31 provided below a process tank 11 is driven toraise the process tank 11 and immerse the separator workpiece 20 in theprocess liquid 71 contained in the process tank 11. 72, 72 are heatersdisposed inside the process tank 11; 73 is a power supply for theheaters 72, 72; and 74 is a temperature sensor for detecting thetemperature of the process liquid 71, and by a temperature signal beingsent from this temperature sensor 74 to the liquid temperature controldevice 41, the liquid temperature control device 41 controls a currentpassing through the heaters 72, 72 from the power supply 73 and adjuststhe temperature of the process liquid 71 to a predetermined temperature.

The lifter 31 is a pantograph type raising and lowering device made upof a base part 76, first bars 78, 78 (the back side first bar 78 is notshown in the figure) each having one end swingably attached to this basepart 76 and the other end slidably attached to a process tank bearingpart 77 provided below the first process tank 11, second bars 79, 79(the back side second bar 79 is not shown in the figure) each having oneend slidably attached to the base part 76 and the other end swingablyattached to the process tank bearing part 77, and a cylinder device (notshown) for driving the first bars 78, 78 or the second bars 79, 79.

An electric motor 82 provided inside the separator carrying part 48 hasa drum 83 on its output shaft and takes in a wire 84 onto this drum 83,and a frame-shaped member 85 is removably attached to the end of thiswire 84 and the separator workpiece 20 is held by this frame-shapedmember 85.

For example, if forward and reverse rotation of the output shaft of theelectric motor 82 are repeated with a separator workpiece 20 immersed inthe process liquid 71, the drum 83 forward and reverse rotates and thewire 84 moves up and down and the separator workpiece 20 moves up anddown along with the frame-shaped member 85, and an effect substantiallythe same as agitating the process liquid 71 is obtained.

As a result, the treatment of the separator workpiece 20 with theprocess liquid 71 can be quickened.

The speed of the electric motor 82 is controlled by the control unit 42by way of the driving device 22. By this means, the speed of the up anddown movement of the separator workpiece 20 can be changed. The speed ofthe up and down movement in this case is an “agitation speed” which willbe discussed later.

The wire 84 is divided into an upper wire 84 a and a lower wire 84 b andthe weight sensor 49 is interposed between the upper wire 84 a and thelower wire 84 b, and to check the weight of the separator workpiece 20the total weight Wt of the lower wire 84 b, the frame-shaped member 85and the separator workpiece 20 is measured with the weight sensor 49 andby this weight signal being sent to the control unit 42 (see FIG. 1) theweight Ws of the separator workpiece 20 is calculated by the weight Wwof the lower wire 84 b and the weight Wf of the frame-shaped member 85being subtracted from the total weight Wt by the control unit 42. Thatis, Ws=Wt−(Ww+Wf).

The main treatments in the production process of a separator areillustrated in order in FIG. 3.

1. Abnormal Layer Removal

A separator workpiece 20 is rolled before being press-formed to apredetermined shape.

When the separator workpiece 20 is rolled, an abnormal layer 91 isformed at the surface of the separator workpiece 20. The abnormal layer91 is a layer where, due to the rolling, particulate materials(intermetallic compounds and so on) which had been included in theseparator workpiece 20 are broken up and their particle size has becomesmaller, and as a result of oxides and the like being included theconductivity has fallen, which raises the electrical contact resistancewhen the separator is stacked and becomes a factor reducing the outputof the fuel cell. 92 . . . denotes particulate conductors, which aregood conductors included in the separator workpiece 20, and include forexample Cr₂B, which is an intermetallic compound. The shapes of theconductors 92 differ, but for convenience the same reference number hasbeen used.

2. Abnormal Layer Removal Etching

The abnormal layer 91 described above is removed by etching. After that,the separator workpiece 20 is weighed, and the removed weight ofabnormal layer 91 is obtained.

3. First Passivation Treatment

To prevent corrosion of the separator workpiece 20 a first passivationtreatment is carried out, and a first passivation film 93 is formed.

4. Exposure Etching

Etching is carried out to remove a surface layer of the separatorworkpiece 20 so that the conductors 92 project (are exposed) from thesurface of the separator workpiece 20. The weight of the separatorworkpiece 20 removed at this time will be called the exposure weight.After that, the separator workpiece 20 is weighed to obtain the exposureweight.

5. Second Passivation Treatment

After the exposure of the conductors 92 a second passivation treatmentis carried out to prevent corrosion of the separator workpiece 20, and asecond passivation film 94 is formed.

This completes the manufacture of the separator.

In FIG. 4, the process including the main treatments described withreference to FIG. 3 is illustrated. STXX indicates a step number. Theparts surrounded by broken lines in the figure are steps related toweight measurement.

ST11 A rolled and then press-formed separator workpiece is degreased.

ST12 The separator workpiece is washed.

ST13 The separator workpiece is dried.

ST14 The weight of the separator workpiece is measured. The weight herewill be called the initial weight W1.

ST15 The abnormal layer that had been formed at the time of rolling isremoved by etching.

ST16 The separator workpiece is washed.

ST17 The first passivation treatment is carried out to prevent corrosionof the separator workpiece.

ST18 The separator workpiece is washed.

ST19 The separator workpiece is dried.

ST20 The weight of the separator workpiece is measured. If the weighthere is written intermediate weight W2, and the weight of abnormal layerremoved is written dw1, then W2=W1−dw1.

ST21 It is determined whether or not the intermediate weight W2 of theseparator workpiece (20) is within a predetermined range, i.e. whetheror not the intermediate weight W2 is in the range between anintermediate lower limit value W3 and an intermediate upper limit valueW4 (whether W3≦W2≦W4).

Before the determination, the relationship between the initial weightW1, the intermediate lower limit value W3, the intermediate upper limitvalue W4 and the weight of abnormal layer removed dw1 mentioned abovewill be explained below.

When W3≦W2≦W4, because W2=W1−dw1, W3≦(W1−dw1)≦W4. From this,(W1-W4)≦dw1≦(W1-W3). This is the range in which the weight of abnormallayer removed dw1 should lie.

In ST21, when the intermediate weight W2 of the separator workpiece doesnot satisfy W3≦W2≦W4 (NO), processing is ended. That is, this separatorworkpiece is removed from the separator production process.

When the intermediate weight W2 of the separator workpiece satisfiesW3≦W2≦W4 (YES), processing proceeds to ST22.

ST22 Etching to expose the conductors in the separator workpiece iscarried out.

ST23 The separator workpiece is washed.

ST24 The separator workpiece is dried.

ST25 The weight of the separator workpiece is measured. When the weighthere is called the post-exposure etching weight W5 and the exposureweight is written dw2, then W5=W2−dw2.

ST26 It is determined whether or not the post-exposure etching weight W5of the separator workpiece is within a predetermined range, i.e. whetheror not the post-exposure etching weight W5 is in the range between apost-exposure etching lower limit value W6 and a post-exposure etchingupper limit value W7 (whether or not W6≦W5≦W7).

Before the determination, the relationship between the intermediateweight W2, the post-exposure etching lower limit value W6, thepost-exposure etching upper limit value W7 and the exposure weight dw2mentioned above will be described below.

When W6≦W5≦W7 is obtained, because W5=W2−dw2, W6≦(W2−dw2)≦W7. From this,(W2-W7)≦dw2≦(W2-W6). This is the range in which the exposure weight dw2should lie.

In ST26, when the post-exposure etching weight W5 of the separatorworkpiece does not satisfy W6≦W5≦W7 (NO), processing is ended. That is,this separator workpiece is removed from the separator productionprocess.

When the post-exposure etching weight W5 of the separator workpiecesatisfies W6≦W5≦W7, processing proceeds to ST27.

ST27 The second passivation treatment is carried out, to preventcorrosion of the separator workpiece.

ST28 The separator workpiece is washed.

ST29 The separator workpiece is dried.

This completes the manufacture of the separator.

The embodiment of a separator production process shown in FIG. 5 differsfrom the metal separator production process shown in FIG. 4 in the timeat which the intermediate weight is measured.

ST31 A rolled and then press-formed separator workpiece is degreased.

ST32 The separator workpiece is washed.

ST33 The separator workpiece is dried.

ST34 The weight of the separator workpiece is measured. The weight herewill be called the initial weight W11.

ST35 The abnormal layer that had been formed at the time of rolling isremoved by etching.

ST36 The separator workpiece is washed.

ST37 The separator workpiece is dried.

ST38 The weight of the separator workpiece is measured. When the weighthere is written intermediate weight W12 and the weight of abnormal layerremoved is written dw11, then W12=W11−dw11.

ST39 It is determined whether or not the intermediate weight W12 of theseparator workpiece is within a predetermined range, i.e. whether or notthe intermediate weight W12 is within the range between an intermediatelower limit value W13 and an intermediate upper limit value W14 (whetheror not W13≦W12≦W14).

Before the determination, the relationship between the initial weightW11, the intermediate lower limit value W13, the intermediate upperlimit value W14 and the weight of abnormal layer removed dw11 mentionedabove will be explained below.

When W13≦W12≦W14 is obtained, because W12=W11−dw11, W13≦(W11−dw11)≦W14.From this, (W11-W14)≦dw11≦(W11-W13). This is the range in which theweight of abnormal layer removed dw11 should lie.

In ST39, when the intermediate weight W12 of the separator workpiecedoes not satisfy W13≦W12≦W14 (NO), processing is ended. That is, thisseparator workpiece is removed from the separator production process.

When the intermediate weight W12 of the separator workpiece does satisfyW13≦W12≦W14 (YES), processing proceeds to ST40.

ST40 The first passivation treatment is carried out, to preventcorrosion of the separator workpiece.

ST41 The separator workpiece is washed.

ST42 Etching is carried out to expose the conductors in the separatorworkpiece.

ST43 The separator workpiece is washed.

ST44 The separator workpiece is dried.

ST45 The weight of the separator workpiece is measured. When the weighthere is written post-etching weight W15 and the exposure weight iswritten dw12, then W15=W12−dw12.

ST46 It is determined whether or not the post-exposure etching weightW15 of the separator workpiece is within a predetermined range, i.e.whether or not the post-exposure etching weight W15 is in the rangebetween a post-exposure etching lower limit value W16 and apost-exposure etching upper limit value W17 (whether or notW16≦W15≦W17).

Before the determination, the relationship between the intermediateweight W12, the post-exposure etching lower limit value W16, thepost-exposure etching upper limit value W17 and the exposure weight dw12mentioned above will be described below.

When W16≦W15≦W17 is obtained, because w15=W12−dw12, W16≦(W12-dw12)≦W17.From this, (W12-W17)≦dw12≦(W12-W16). This is the range in which theexposure weight dw12 should lie.

In ST46, when the exposure etching weight W15 does not satisfyW16≦W15≦W17 (NO), processing is ended. That is, this separator workpieceis removed from the separator production process.

When the etching weight W15 of the separator workpiece does satisfyW16≦W15≦W17 (YES), processing proceeds to ST47.

ST47 The second passivation treatment is carried out to preventcorrosion of the separator workpiece.

ST48 The separator workpiece is washed.

ST49 The separator workpiece is dried.

This completes the manufacture of the separator.

As shown in FIG. 6, a separator manufacturing apparatus 100 is made upof a first process tank 11 (the process tank 11 mentioned above willfrom now on be referred to as the first process tank 11) and a secondprocess tank 12 through a sixth process tank 16 holding process liquidsfor carrying out treatments relating to separator production which willbe further discussed later, a dryer 17, a carrying apparatus 121 forcarrying a separator workpiece 20 to become a separator to the positionsof the first process tank 11 through the sixth process tank 16 and thedryer 17, a driving device 22 for driving an electric motor for raisingand lowering a separator workpiece 20 carried by this carrying apparatus121, a first lifter 31 (the lifter 31 mentioned above will from now onbe referred to as the first lifter 31) and a second lifter 32 through asixth lifter 36 for raising and lowering the first process tank 11through the sixth process tank 16 respectively to immerse the separatorworkpiece 20 in the process liquids of the first process tank 11 throughthe sixth process tank 16, the liquid temperature control devices 41 . .. (although the first process tank 11 through the sixth process tank 16are each provided with one of these liquid temperature control devices41, in the figure one is drawn only on the first process tank 11) forcontrolling the temperatures of the process liquids in the first processtank 11 through the sixth process tank 16, and a control unit 42 forcontrolling the dryer 17, the carrying apparatus 121, the driving device22, the first lifter 31 through the sixth lifter 36, and the liquidtemperature control devices 41. 31 d through 36 d are lifter drivers fordriving the respective first lifter 31 through sixth lifter 36. Thesecond lifter 32 through the sixth lifter 36 and the lifter drivers 32 dthrough 36 d are of the same construction as the first process tank 11and the lifter driver 31 d.

The above-mentioned first process tank 11 is a degreasing tank, thesecond process tank 12, the fourth process tank 14 and the sixth processtank 16 are washing tanks, the third process tank 13 is an etching tank,and the fifth process tank 15 is a passivation process tank.

The third process tank 13 is made up of three tanks lined up in thefront-rear direction of the paper, namely an A-tank 13 a, a B-tank 13 band a C-tank 13 c, and the third lifter 33 also is made up of anA-lifter, a B-lifter and a C-lifter, not shown in the figure,corresponding to the A-tank 13 a, the B-tank 13 b and the C-tank 13 c.

The carrying apparatus 121 is made up of a first drum 44, a second drum46, a cable 47 and a separator carrying part 48.

The third lifter 33 also has a horizontal moving mechanism (not shown)for moving the A-tank 13 a, the B-tank 13 b and the C-tank 13 cintegrally in the front-rear direction of the paper, and by the A-tank13 a, the B-tank 13 b or the C-tank 13 c being moved to directly belowthe separator workpiece 20 and lifted, the separator workpiece 20 can beselectively immersed in the A-tank 13 a, the B-tank 13 b or the C-tank13 c.

In FIG. 7, a separator manufacturing method of a second embodiment isillustrated.

ST51 A separator workpiece is degreased. The process liquid is anaqueous surfactant solution, the temperature of the process liquid is30° C., and the treatment time is 1 minute.

ST52 The separator workpiece is washed. The treatment time p. 20 is 1minute.

ST53 An etching is carried out to remove the abnormal layer formed onthe separator workpiece and to expose the conductors included in thesurface layer of the separator workpiece. The process liquid is asolution of 10% nitric acid and 4% hydrofluoric acid, the process liquidtemperature is 60° C. and the treatment time is 40 minutes.

ST54 The separator workpiece is washed. The time required is 1 minute.

ST55 A passivation treatment is carried out on the surface of theseparator workpiece, and a passivation film is formed. The processliquid is 50% nitric acid, the process liquid temperature is 50° C. andthe treatment time is 30 minutes.

ST56 The separator workpiece is washed. The treatment time is 1 minute.

ST57 The separator workpiece is dried. The time required is 1 minute.

This completes the manufacture of the separator. The time required forthe above production is 75 minutes in total, and is 62 minutes shorterthan the total of 137 minutes required for the related art describedwith reference to FIG. 22.

The process steps described above are carried out with the separatorworkpiece being moved to the positions of the respective process tanksand the dryer.

That is, the degreasing of ST51 is carried out in the position of thefirst process tank, the washing of ST52 in that of the second processtank, the etching of ST53 in that of the third process tank, the washingof ST54 in that of the fourth process tank, the passivation treatment ofST55 in that of the fifth process tank, the washing of ST56 in that ofthe sixth process tank, and the drying of ST57 in that of the dryer.

With reference to FIG. 8A through FIG. 8C, the removal of the abnormallayer from the separator workpiece (ST53), the exposure of conductors(ST53) and the passivation treatment (ST55) will now be explained indetail.

FIG. 8A shows an abnormal layer 91 formed on a separator workpiece 20.

To remove this abnormal layer 91, first, etching is carried out (seeST53 of FIG. 7). As a result of this, as shown in FIG. 8B, as well asthe abnormal layer 91 disappearing, a surface layer of the separatorworkpiece 20 itself is removed, and the conductors 92 . . . are causedto project; that is, exposing of the conductors 92 . . . is effected.

Then, to prevent corrosion of the surface of the separator workpiece 20itself, other than the conductors 92 . . . , a passivation treatment(see ST55 of FIG. 7) is carried out, and as shown in FIG. 8C apassivation film 95 is formed on the surface of the separator workpiece20 itself. At this time, the passivation film 95 is not formed on thesurfaces of the conductors 92 . . . , and because the conductors 92 . .. have a large surface area and project from the passivation film 95,when the separator is stacked, the contact resistance between adjacentseparators and between separators and electrodes can be made low.

With reference to FIG. 9A through FIG. 9D, the removal of the abnormallayer and the exposing of the conductors described with reference toFIG. 8A through FIG. 8C will now be explained in further detail.

FIG. 9A is an enlarged sectional view of a main part of a separatorworkpiece with an abnormal layer 91 formed on the separator workpiece20.

The thickness of the abnormal layer 91 varies with the state of therolling. For example, there is the case where the thickness of theabnormal layer 91 is T1, the case where the thickness is T2, and thecase where the thickness is T3. In the range [1] where the thickness isT1 to T2, if the surface is examined with a metal microscope, it appearsas shown in FIG. 9B. That is, the conductors 92 cannot be observed.

And in the range [2] where the thickness of the abnormal layer 91 is T2to T3, if the surface is examined with a metal microscope, it appears asshown in FIG. 9C. That is, there are from conductors 92 which can onlyjust be seen to conductors 92 which can be observed at a particle sizeof up to 2 μm.

Also, in the range [3] where the thickness of the abnormal layer 91 isless than T3 and greater than T=0, when the surface is examined with ametal microscope, it appears as shown in FIG. 9D. That is, the particlediameters of the conductors 92 exceed 2 μm and can be observed at sizesof up to 20 μm.

In practice, the above-mentioned thickness T1 is about 5 μm, thethickness T2 is about 21 μm and the thickness T3 is about 0.5 μm.

In this invention, the conditions of the etching for removing theabnormal layer 91 and exposing the conductors 92, namely theconstituents of the process liquid, the process liquid temperature, theagitation method (speed etc.) and the treatment time, are changedaccording to the thickness of the abnormal layer 91.

Specifically, according to the thickness of the abnormal layer 91described above, one tank is selected from among the A-tank 13 a, theB-tank 13 b and the C-tank 13 c of the third process tank 13 shown inFIG. 6 and the separator is immersed in this and processed undertreatment conditions corresponding to that tank.

A first practicing mode of these etching conditions will now bedescribed, with reference to the columns of Mode 1 of the followingtable. Solution Treatment Solution Temp. Agitation Time Mode ConditionsComposition ° C. m/min min 1 Embodiment A1 10% nitric 8% hydrofluoric 7010 60 acid acid Embodiment B1 20% nitric 4% hydrofluoric 50 5 30 acidacid Embodiment C1 30% nitric 2% hydrofluoric 30 0.6 10 acid acid 2Embodiment A2 10% nitric 8% hydrofluoric 70 5 30 acid acid Embodiment B220% nitric 4% hydrofluoric 50 5 30 acid acid Embodiment C2 30% nitric 2%hydrofluoric 30 5 30 acid acid 3 Embodiment A3 10% nitric 4%hydrofluoric 60 10 40 acid acid Embodiment B3 10% nitric 4% hydrofluoric60 5 20 acid acid Embodiment C3 10% nitric 4% hydrofluoric 60 1 5 acidacid 4 Embodiment A4 10% nitric 8% hydrofluoric 60 10 40 acid acidEmbodiment B4 10% nitric 4% hydrofluoric 60 5 20 acid acid Embodiment C410% nitric 2% hydrofluoric 60 1 5 acid acid

Mode 1:

Embodiment A1: The solution composition, i.e. the constituents of theprocess liquid, is a solution of 10% nitric acid and 8% hydrofluoricacid; the solution temperature, i.e. the temperature of the processliquid, is 70° C.; the agitation speed of the process liquid is 10m/min; and the treatment time is 60 min.

Embodiment B1: The solution composition is a solution of 20% nitric acidand 4% hydrofluoric acid; the solution temperature is 50° C.; theagitation speed is 5 m/min; and the treatment time is 30 min.

Embodiment C1: The solution composition is a solution of 30% nitric acidand 2% hydrofluoric acid; the solution temperature is 30° C.; theagitation speed is 0.6 m/min; and the treatment time is 10 min.

Embodiment A1 is the etching conditions of the A-tank 13 a, EmbodimentB1 those of the B-tank 13 b, and Embodiment C1 those of the C-tank 13 c.

This Mode 1 is etching conditions wherein the greater is the thicknessof the abnormal layer, as shown above, the smaller is the nitric acidconcentration and the larger is the hydrofluoric acid concentration, thehigher is the solution temperature, the higher is the agitation speedand the longer is the treatment time.

Next, a second practicing mode will be described, with reference to thecolumns of Mode 2 of the foregoing table.

Mode 2:

Embodiment A2: The solution composition is a solution of 10% nitric acidand 8% hydrofluoric acid; the solution temperature is 70° C.; theagitation speed is 5 m/min; and the treatment time is 30 min.

Embodiment B2: The solution composition is a solution of 20% nitric acidand 4% hydrofluoric acid; the solution temperature is 50° C.; theagitation speed is 5 m/min; and the treatment time is 30 min.

Embodiment C2: The solution composition is a solution of 30% nitric acidand 2% hydrofluoric acid; the solution temperature is 30° C.; theagitation speed is 5 m/min; and the treatment time is 30 min.

Embodiment A2 is the etching conditions of the A-tank 13 a, EmbodimentB2 those of the B-tank 13 b, and Embodiment C2 those of the C-tank 13 c.

This Mode 2 is etching conditions wherein the greater is the thicknessof the abnormal layer, as shown above, the smaller is the nitric acidconcentration and the larger is the hydrofluoric acid concentration, andthe higher is the solution temperature.

Next, a third practicing mode will be described, with reference to thecolumns of Mode 3 of the foregoing table.

Mode 3:

Embodiment A3: The solution composition is a solution of 10% nitric acidand 4% hydrofluoric acid; the solution temperature is 60° C.; theagitation speed is 10 m/min; and the treatment time is 40 min.

Embodiment B3: The solution composition is a solution of 10% nitric acidand 4% hydrofluoric acid; the solution temperature is 60° C.; theagitation speed is 5 m/min; and the treatment time is 20 min.

Embodiment C3: The solution composition is a solution of 10% nitric acidand 4% hydrofluoric acid; the solution temperature is 60° C.; theagitation speed is 1 m/min; and the treatment time is 5 min.

Embodiment A3 is the etching conditions of the A-tank 13 a, EmbodimentB3 those of the B-tank 13 b, and Embodiment C3 those of the C-tank 13 c.

This Mode 3 is etching conditions wherein the greater is the thicknessof the abnormal layer, as shown above, the higher is the process liquidagitation speed and the longer is the treatment time.

Next, a fourth practicing mode will be described, with reference to thecolumns of Mode 4 of the foregoing table.

Mode 4:

Embodiment A4: The solution composition is a solution of 10% nitric acidand 8% hydrofluoric acid; the solution temperature is 60° C.; theagitation speed is 10 m/min; and the treatment time is 40 min.

Embodiment B4: The solution composition is a solution of 10% nitric acidand 4% hydrofluoric acid; the solution temperature is 60° C.; theagitation speed is 5 m/min; and the treatment time is 20 min.

Embodiment C4: The solution composition is a solution of 10% nitric acidand 2% hydrofluoric acid; the solution temperature is 60° C.; theagitation speed is 1 m/min; and the treatment time is 5 min.

Embodiment A4 is the etching conditions of the A-tank 13 a, EmbodimentB4 those of the B-tank 13 b, and Embodiment C4 those of the C-tank 13 c.

This Mode 4 is etching conditions wherein the greater is the thicknessof the abnormal layer, as shown above, the greater is the hydrofluoricacid concentration, the higher is the agitation speed, and the longer isthe treatment time.

As shown in FIG. 10, a granular agitating material 97 . . . whichpromotes etching, for example silicon carbonate (SiC), is mixed with theprocess liquid 71 of the separator workpiece 20.

When in this state the separator workpiece 20 is moved up and down, thegrains of agitating material 97 . . . hit the surface of the separatorworkpiece 20 and perform the role of a polisher, whereby it is possibleto quicken the removal of the abnormal layer of the separator workpiece20 and the exposing of the conductors.

A separator manufacturing apparatus 200 of a third embodiment shown inFIG. 11 is made up of a first process tank 11 through a sixth processtank 16 and a dryer 17, a carrying apparatus 221 serving as carryingmeans for carrying a plurality of separator workpieces 20 . . . to thepositions of the first process tank 11 through the sixth process tank 16and the dryer 17, a driving part 22 for driving an electric motor forraising and lowering the separator workpieces 20 moved by this carryingapparatus 221, a first lifter 31 through a sixth lifter 36, liquidtemperature control devices 41 . . . , and a control unit 42 forcontrolling the carrying apparatus 221.

The carrying apparatus 221 is made up of a first drum 44, a second drum46, a cable 47, a separator carrying part 48, and a cylindrical holdingjig 50 for holding the separator workpieces 20.

As shown in FIG. 12, the cylindrical holding jig 50 is a member mountedby attaching a shaft 53 to the output shaft of an electric motor 51 byway of a joint 52 and screwing a nut 54 onto a male thread 53 a providedon this shaft 53, and the separator workpieces 20 . . . are held on thecircumferential face of the cylindrical holding jig 50. 53 b is a flangeformed integrally with the shaft 53, and 55 is a washer.

The cylindrical holding jig 50, the joint 52, the shaft 53 and the nut54 are members made of a material which does not react with the processliquids, or are members surface-treated so that they do not react withthe process liquids.

The structure which holds the separator workpiece 20 will be explainedwith reference to the next figure.

As shown in FIG. 13, the cylindrical holding jig 50 is made up of acylinder part 57 and frame members 58 . . . mounted to thecircumferential face 57 a of the cylinder part 57 and uniformly spacedin the circumferential direction to hold the separator workpieces 20. 57b is a through hole for the shaft 53 (see FIG. 12) to pass through.

The frame members 58 are each made up of a U-shaped frame proper 61 anda top fitting member 62 which fits to the top of this frame proper 61.

Each frame proper 61 is made up of a cylinder-mounted part 64 mounted tothe cylinder part 57, a frame bottom part 65 extending outward from thebottom end of this cylinder-mounted part 64, and a parallel part 66which rises from this frame bottom part 65 and is parallel with thecylinder-mounted part 64.

As shown in FIG. 14A, the frame proper 61 of each of the frame members58 has a separator insertion groove 61 a formed in the cylinder-mountedpart 64, the frame bottom part 65 (see FIG. 13) and the parallel part 66for inserting the edge of a separator workpiece 20 into, and cutaways 61b, 61 b formed in the upper ends of the cylinder-mounted part 64 and theparallel part 66.

The top fitting member 62 has plate-shaped insertable parts 62 a, 62 awhere it is formed into a plate shape and the plate thickness is madesmaller than around there, for insertion into the separator insertiongroove 61 a in the frame proper 61, and fitting parts 62 b, 62 bprojecting from the plate-shaped insertable parts 62 a, for fitting intothe cutaways 61 b, 61 b in the frame proper 61.

By the cutaways 61 b, 61 b being provided in the frame proper 61 and thefitting parts 62 b, 62 b being provided on the top fitting member 62like this, the cylinder-mounted part 64 and the top fitting member 62,and the parallel part 66 and the top fitting member 62, can be fittedtogether surely.

FIG. 14B shows a separator workpiece 20 fitted in the separatorinsertion groove 61 a in the frame proper 61 of a frame member 58 and atop fitting member 62 fitted to the top of the frame proper 61.

In this state, for example even if an external force F acts in thedirection of the arrow on the parallel part 66 of the frame proper 61,because the cylinder-mounted part 64 and the parallel part 66 of theframe proper 61 are mated with the top fitting member 62, the frameproper 61 is strong and can be prevented from deforming.

FIG. 15 shows for example the first lifter 31 having been driven toraise the first process tank 11 with respect to separator workpieces 20. . . held by the cylindrical holding jig 50 to immerse the separatorworkpieces 20 . . . in the process liquid 71.

The electric motor 51 and the driving part 22 constitute a cylindricalholding jig driving device 75 serving as driving means for driving, i.e.rotating, the cylindrical holding jig 50.

For example, with the separator workpieces 20 immersed in the processliquid 71, if the output shaft of the electric motor 51 is rotated in afixed direction, or if forward and reverse rotation are repeated, theseparator workpieces 20 . . . rotate along with the cylindrical holdingjig 50 and agitate the process liquid 71. As a result, the treatment ofthe separator workpieces 20 with the process liquid 71 can be quickened,and also by the agitation of the process liquid 71 the process liquid 71becomes uniform inside the first process tank 11, and the treatment ofthe separator workpieces 20 can be carried out evenly.

The flow of the separator manufacturing method of this third embodimentis the same as the flow of ST51 through ST57 shown in FIG. 7. Aseparator manufacturing apparatus 300 of a fourth embodiment shown inFIG. 16 is made up of a first process tank 11 through a fourth processtank 14 and a dryer 17, a carrying apparatus 321 for carrying separatorworkpieces 20 constituting metal materials to become separators to thepositions of the first process tank 11 through the fourth process tank14 and the dryer 17, a first lifter 31 through a fourth lifter 34,liquid temperature control devices 41 . . . (although the first processtank 11 through the fourth process tank 14 are each provided with one ofthese liquid temperature control devices 41, in the figure one has beendrawn only on the first process tank 11), an electricity supply 337serving as electricity supplying means for supplying electricity to anelectrode inserted into the process liquid in the third process tank 13(the details of this will be discussed later) and a separator workpiece20 immersed in the process liquid in the same third process tank 13, anda control unit 338 serving as electrical potential control means forcontrolling the dryer 17, the carrying apparatus 321, the first lifter31 through the fourth lifter 34, the liquid temperature control devices41 and the electricity supply 337. 341 is a timer provided in thecontrol unit 338.

The above-mentioned first process tank 11 is a degreasing tank, thesecond process tank 12 and the fourth process tank 14 are washing tanksfor rinsing with water, and the third process tank 13 is an electrolyticetching and passivation treatment tank (the details of which will bediscussed later).

The dryer 17 is a device operated and stopped by an ON/OFF signal fromthe control unit 338.

The carrying apparatus 321 is made up of a first drum 44, a second drum46, a cable 47, and a separator carrying part 348 attached to this cable47.

The timer 341 is for supplying to the control unit 338 a time signal forsetting a treatment time of the electrolytic etching and passivationtreatment carried out in the third process tank 13.

FIG. 17 shows for example the third lifter 33 having been driven toraise the third process tank 13 with respect to a separator workpiece 20and immerse the separator workpiece 20 in a process liquid 349 containedin the third process tank 13.

The separator workpiece 20 is attached to a T-shaped separator holdingmember 352 by fasteners 353, 353, and this separator holding member 352is attached to the separator carrying part 348 by a wire 354. 355 is acontact point part provided on the separator holding member 352 so as tomake contact with the separator workpiece 20, and is a part forsupplying electricity from the electricity supply 337.

357, 357 are electrodes provided in the third process tank 13 so as tobe immersed in the process liquid 349, and by electricity being suppliedfrom the electricity supply 337 to these electrodes 357, 357 and theabove-mentioned separator workpiece 20, electrolytic etching and apassivation treatment, which will be discussed later, are carried out onthe separator workpiece 20 in the third process tank 13. The supply ofcurrent is carried out by the electricity supply 337 being connected asa d.c. power source so that the separator workpiece 20 becomes an anodeand the electrodes 357, 357 become cathodes.

358 is a current density detecting device serving as current densitydetecting means which has an ammeter for detecting the current value ofwhen electricity is supplied from the electricity supply 337 to theseparator workpiece 20 and the electrodes 357, 357 and obtains a currentvalue per unit area, i.e. a current density, from the current valuedetected with this ammeter and the surface area of one of the electrodeplates 357.

361 is an air agitating device disposed at the bottom of the thirdprocess tank 13 for agitating the process liquid 349 by continuouslymaking air bubbles.

In FIG. 18, the flow of the separator manufacturing method of the fourthembodiment is explained.

ST61 A separator workpiece is degreased. The process time is 1 minute.

ST62 The separator workpiece is washed. The process time is 1 minute.

ST63 Electrolytic etching is carried out to remove the abnormal layerformed on the separator workpiece and to expose conductors included inthe surface layer part of the separator workpiece.

The process liquid is a solution made up of 30% phosphoric acid, 25%sulfuric acid, 10% nitric acid, 5% hydrogen peroxide, 1% surfactant andthe rest water (the respective units are weight %), the temperature ofthe process liquid is 40° C., the current density during electricitysupply to the separator workpiece and the electrodes is 18 A/dm² fixed,the agitating method is air agitation, and the process time is 10minutes.

ST64 With the potential difference between the separator workpiece andthe electrodes made a constant 1 V, a passivation treatment is carriedout on the surface of the separator workpiece and a passivation film isformed.

The temperature of the process liquid is 40° C., and the process time is20 minutes. The constituents of the process liquid, the temperature andthe agitation method are the same as in ST63.

ST65 The separator workpiece is washed. The process time is 1 minute.

ST66 The separator workpiece is dried. The required time is 1 minute.

This completes the manufacture of the separator. The time required forthe manufacture described above is 34 minutes, and is 103 minutesshorter than the 137 minutes required for the related art described withreference to FIG. 22.

The process steps described above are carried out with the separatorworkpiece being moved to the positions of the respective process tanksand the dryer.

That is, the degreasing of ST61 is carried out in the position of thefirst process tank, the washing of ST62 in that of the second processtank, the electrolytic etching of ST63 and the passivation treatment ofST64 in that of the third process tank, the washing of ST65 in that ofthe fourth process tank, and the drying of ST66 in that of the dryer.

By the process steps described above, in the same way as that shown inFIG. 8A through FIG. 8C, abnormal layer removal and conductor exposureare carried out by electrolytic etching and then a passivation film isformed by a passivation treatment.

In FIG. 19, the relationship between the potential difference and thecurrent density of the electrolytic etching and passivation treatmentexplained with FIG. 18 is illustrated with a graph. The vertical axis ofthe graph shows the current density obtained with the current densitydetecting device 358 (the units are A/dm²), and the horizontal axisshows the potential difference between the separator workpiece 20 andthe electrodes 357 (the units are V).

In the range of potential difference applied between the separatorworkpiece and the electrodes up to an upper limit of about 6V, even whenthe potential difference is increased, the current density increasesvery little.

This is because while the potential difference is small a passive filmof an insulating or almost insulating nature, which is a metal oxidefilm, forms on the surface of the separator workpiece, and this passivefilm makes it difficult for current to flow. This range of potentialdifference is called the passive region.

When the potential difference is made larger than the passive region,the current density sharply increases.

This is because current is expended on both oxygen production anddissolving of the separator workpiece (the abnormal layer and theseparator workpiece itself), and furthermore the rate of dissolvingbecomes higher than the forming of the metal oxide film. This range ofpotential difference is called the super-passive region.

Accordingly, if the above-mentioned super-passive region is used for theelectrolytic etching, removal of the abnormal layer of the separatorworkpiece and removal of the surface of the separator workpiece itselffor conductor exposure can be carried out. And by using theabove-mentioned passive region for the passivation treatment, apassivation film can be formed.

In the electrolytic etching, the potential difference Ve is adjusted,that is, potential-controlled, for example so that the current densitybecomes a constant 18 A/dm².

In the passivation treatment, for example the potential difference iskept at a constant 1 V.

In FIG. 20, a construction for the potential control of the electrolyticetching and the passivation treatment is illustrated.

A potential control device 395 of the separator manufacturing apparatus300 is made up of the timer 341 (see also FIG. 16) for generating thetime signal ST, potential control means 338 (in fact the control unit338 (see FIG. 16)) for setting the treatment times of the electrolyticetching and the passivation treatment on the basis of the time signal STfrom this timer 341 and controlling the potential difference for theelectrolytic etching and the passivation treatment, electricity supplymeans 337 (in fact the electricity supply 337 (see FIG. 16)) forsupplying electricity to the separator workpiece 20 and the electrodes357 in accordance with a control signal SC from this potential controlmeans 338, and current density detecting means 358 (in fact the currentdensity detecting device 358 (see FIG. 17)) for detecting the currentdensity when electricity is supplied by this electricity supply means337 and supplying a current density signal SD to the potential controlmeans 338 on the basis of the detected current density.

At the time of the electrolytic etching, when electricity is suppliedfrom the electricity supply means 337 to the separator workpiece 20 andthe electrodes 357, on the basis of the current density detected by thecurrent density detecting means 358 at this time, the potential controlmeans 338 controls the electricity supply means 337 so that thepotential difference between the separator workpiece 20 and theelectrodes 357 is 18 V/dm².

For example, if the current density detected by the current densitydetecting means 358 is smaller than 18 V/dm², the potential controlmeans 338 controls the electricity supply means 337 to increase thecurrent density so that the potential difference between the separatorworkpiece 20 and the electrodes 357 increases, and if the detectedcurrent density is greater than 18 V/dm², the potential control means338 controls the electricity supply means 337 to decrease the currentdensity so that the potential difference between the separator workpiece20 and the electrodes 357 decreases, and the current density is therebykept at a constant 18 V/dm².

At the time of the passivation treatment, the potential control means338 controls the electricity supply means 337 so that the potentialdifference between the separator workpiece 20 and the electrodes 357 isa constant 1 V.

The weight measuring means of this invention is not limited to one of atype like the weight sensor 49 shown in FIG. 1, and alternatively it maybe one installed on a work table or the like, separately from theseparator workpiece carrying apparatus.

Although in FIG. 13 the frame members 58 were each made up of acylinder-mounted part 64 and a frame bottom part 65 and a parallel part66, there is no limit to this, and alternatively the frame members mayeach be made up of a frame bottom part 65 extending outward from thecylinder part 57 and a parallel part 66 and a groove for inserting theedge of a separator may be formed in the circumferential face 57 a ofthe cylinder part 57 and the top fitting member 62 may be fitted to thetop ends of the cylinder part 57 and the parallel part 66.

Also, although the electrolytic etching step and the passivationtreatment step following this step were carried out consecutively in thesame process tank using potential control, there is no limit to this,and alternatively the electrolytic etching step and the passivationtreatment step may be carried out using potential control consecutivelyin different process tanks filled with different process liquids.

INDUSTRIAL APPLICABILITY

The fuel cell separator manufacturing method of this invention includesan abnormal layer removal step of removing an abnormal layer which formsat the surface layer of a metal material for use as separator when it isrolled and becomes a cause of conductivity decrease, a conductorexposing step of causing portions of conducting matter constituting goodconductors naturally included in the surface layer part of the metalmaterial itself to project, and a passivation treatment step ofperforming a passivation treatment on the surface layer part of themetal material itself. As a result, abnormal layer removal and conductorexposure for lowering the electrical contact resistance of the metalmaterial and raising its resistance to corrosion can be carried outchemically or electro-chemically in the same process, and the number ofprocess steps can be cut. Thus, the invention is useful in themanufacture of fuel cells and other electrical components (for exampleprimary cells, secondary cells, capacitors) in which surface treatmentof a metal material is necessary.

1. A fuel cell separator manufacturing method comprising: a step ofrolling with rolling means a metal material to be used as a fuel cellseparator; a step of forming the rolled material into a predeterminedshape with pressing means; an abnormal layer removing step of removingan abnormal layer arising at the surface of the metal material when itis rolled and press-shaped; a conductor exposing step of causingportions of conductors included in a surface layer part of the metalmaterial to project; and a passivation treatment step of carrying out apassivation treatment on the surface layer part of the metal material,wherein the method further comprises a step of determining a thicknessof the abnormal layer by examination of the conductors, and the abnormallayer removing step and the conductor exposing step are carried out in asingle etching with a temperature, composition, concentration andagitation of an etching liquid selected in correspondence with thethickness of the abnormal layer.
 2. (canceled)
 3. (canceled) 4.(canceled)
 5. (canceled)
 6. The fuel cell separator manufacturing methodaccording to claim 1, wherein the etching is carried out in a liquidtank selected, in correspondence with a state of the abnormal layer,from a plurality of liquid tanks holding etching liquids of differentcompositions.
 7. The fuel cell separator manufacturing method accordingto claim 1, wherein the removal of the abnormal layer is promoted bygranular materials mixed with the etching liquid and the etching liquidbeing agitated.
 8. The fuel cell separator manufacturing methodcomprising: an abnormal layer removing step of removing an abnormallayer arising at the surface of a metal material to be used as aseparator when it is rolled; a conductor exposing step of causingportions of conductors included in a surface layer part of the metalmaterial to project; and a passivation treatment step of carrying out apassivation treatment on the surface layer part of the metal material,wherein the method further comprises: a first checking step of checkinga weight of the metal material after the abnormal layer is removed; afirst passivation treatment step of carrying out a passivation treatmentfor corrosion resistance on the metal material, the conductor exposingstep being carried out by etching; a second checking step of checkingthe weight of the metal material after the conductor exposing step; anda second passivation treatment step of subsequently carrying out apassivation treatment again, whereby the metal material weight isconfirmed respectively in the first checking step and the secondchecking step.
 9. The fuel cell separator manufacturing method accordingto claim 8, wherein the first checking step and the second checking stepare carried out after the metal material is washed and dried.
 10. Thefuel cell separator manufacturing method according to claim 8, wherein,in that in the case of a metal material whose weight obtained in thefirst checking step or the second checking step falls outside apredetermined range, the subsequent steps are not carried out.
 11. Thefuel cell separator manufacturing method according to claim 8, whereinthe determination of whether the weight obtained in the first checkingstep and the second checking step is within a predetermined range iscarried out by automatic determining means.
 12. A fuel cell separatormanufacturing method comprising: an abnormal layer removing step ofremoving an abnormal layer arising at the surface of a metal material tobe used as a separator when it is rolled; a conductor exposing step ofcausing portions of conductors included in a surface layer part of themetal material to project; and a passivation treatment step of carryingout a passivation treatment on the surface layer part of the metalmaterial, wherein the method further comprises: a step of press-formingthe rolled metal material to a predetermined shape; a step of holding aplurality of such press-formed metal materials on a cylindrical holdingjig by causing the metal materials to be fitted in frame membersprovided on an outer face of the holding jig in a circumferentiallyuniformly spaced relation; a step of immersing the held metal materialsin a process liquid contained in a process tank and agitating theprocess liquid with the metal material by driving the holding jig withdriving means; and a step of removing the metal materials from theprocess tank and drying the materials, whereby the metal materials areheld by the holding members during transfer from one process tank toanother and processed at each process tank without being removed fromthe holding members.
 13. (canceled)
 14. The fuel cell separatormanufacturing method according to claim 1, further comprising: a step ofrolling the metal material with rolling means; a step of forming therolled material to a predetermined shape with pressing means; theabnormal layer removing step; the conductor exposing step; and thepassivation treatment step, and the abnormal layer removing step and theconductor exposing step are carried out by electrolytic etching andwherein the electrolytic etching step and the passivation treatment stepare carried out consecutively using electrical potential control. 15.The fuel cell separator manufacturing method according to claim 14,wherein the potential control, when the metal material is made an anodeand an electrode facing this anode is made a cathode, makes thepotential difference between the anode and the cathode large in theelectrolytic etching step and makes the potential difference between theanode and the cathode small in the passivation treatment step.
 16. Thefuel cell separator manufacturing method according to claim 15, wherein,in the electrolytic etching step, as well as the potential differencebetween the anode and the cathode being made large, the current densityis kept constant.
 17. An apparatus for manufacturing a fuel cellseparator by press-forming a rolled metal material to a predeterminedshape, removing by etching an abnormal layer arising in the metalmaterial as the metal material is rolled, causing portions of conductorsincluded in a surface layer part of the metal material to project, andcarrying out a passivation treatment on the surface layer part of themetal material, the apparatus comprising: a degreasing tank fordegreasing the rolled metal material; an etching tank for carrying outthe etching; a passivation treatment tank for carrying out thepassivation treatment; cleaning tanks for removing respective processliquids from the metal material after the degreasing, the etching andthe passivation treatment; a cylindrical holding jig with frame membersprovided on an outer face thereof in a circumferentially uniformlyspaced relation to hold a plurality of metal materials to be processedin the etching tank, the passivation treatment tank and the cleaningtanks; driving means for driving the cylindrical holding jig to agitateprocess liquids of the etching tank and the passivation treatment tankwith the metal materials held in the holding jig; carrying means forcarrying the cylindrical holding jig to the etching tank and thepassivation treatment tank; and a control unit for controlling thecarrying apparatus and the driving device.
 18. The fuel cell separatormanufacturing apparatus according to claim 17, wherein the manufacturingapparatus comprises an abnormal layer removal tank for removing theabnormal layer, a passivation treatment tank for carrying out thepassivation treatment, a conductor exposing tank for carrying out theexpo-sure of conductors, weight measuring means for measuring a weightof the metal material after the abnormal layer removal and after theconductor exposure, and automatic determining means for determining,based upon weight information from the weight measuring means, whetherthe weight is in a predetermined range.
 19. (canceled)
 20. The fuel cellseparator manufacturing apparatus according to claim 17, wherein themanufacturing apparatus comprises a process tank filled with a processliquid and having an electrode provided in the process liquid toelectrolytically etch the metal material, electricity supply means forsupplying electricity to a metal material immersed in the process liquidin this process tank and the electrode, current density detecting meansfor detecting the current density during the supply of electricity withthis electricity supply means, potential control means for controllingthe potential difference between the metal material and the electrode incorrespondence with the current density detected by this current densitydetecting means, and a timer for sending a time signal to the potentialcontrol means to effect electricity supply for a predetermined time. 21.The fuel cell separator manufacturing method according to claim 9,wherein, in the case of a metal material whose weight obtained in thefirst checking step or the second checking step falls outside apredetermined range, the subsequent steps are not carried out.
 22. Thefuel cell separator manufacturing method according to claim 9, whereinthe determination of whether the weight obtained in the first checkingstep and the second checking step is within a predetermined range iscarried out by automatic determining means.